Update this page to describe modern interfaces.
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Gleb Smirnoff
parent
33fd7c5628
commit
9aa3cab968
@ -28,160 +28,163 @@
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.\"
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.\" $FreeBSD$
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.\"
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.Dd December 11, 2008
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.Dd December 14, 2011
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.Dt RTALLOC 9
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.Os
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.Sh NAME
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.Nm rtalloc ,
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.Nm rtalloc_ign ,
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.Nm rtalloc1 ,
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.Nm rtfree
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.Nm rtalloc1_fib ,
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.Nm rtalloc_ign_fib ,
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.Nm rtalloc_fib
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.Nd look up a route in the kernel routing table
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.Sh SYNOPSIS
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.In sys/types.h
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.In sys/socket.h
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.In net/route.h
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.Ft void
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.Fn rtalloc "struct route *ro"
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.Ft void
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.Fn rtalloc_ign "struct route *ro" "u_long flags"
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.Ft "struct rtentry *"
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.Fn rtalloc1 "struct sockaddr *sa" "int report" "u_long flags"
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.Fn rtalloc1_fib "struct sockaddr *dst" "int report" "u_long flags" "u_int fibnum"
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.Ft void
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.Fn rtfree "struct rt_entry *rt"
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.Fn rtalloc_fib "struct route *ro" "u_int fibnum"
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.Ft void
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.Fn rtalloc_ign_fib "struct route *ro" "u_long flags" "u_int fibnum"
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.Fn RTFREE_LOCKED "struct rt_entry *rt"
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.Fn RTFREE "struct rt_entry *rt"
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.Fn RT_LOCK "struct rt_entry *rt"
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.Fn RT_UNLOCK "struct rt_entry *rt"
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.Fn RT_ADDREF "struct rt_entry *rt"
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.Fn RT_REMREF "struct rt_entry *rt"
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.Ft void
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.Fn rtfree "struct rt_entry *rt"
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.Ft "struct rtentry *"
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.Fn rtalloc1 "struct sockaddr *dst" "int report" "u_long flags"
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.Ft void
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.Fn rtalloc "struct route *ro"
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.Ft void
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.Fn rtalloc_ign "struct route *ro" "u_long flags"
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.Pp
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.Cd options RADIX_MPATH
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.Sh DESCRIPTION
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The kernel uses a radix tree structure to manage routes for the
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networking subsystem.
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If compiled with
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.Cd options RADIX_MPATH
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kernel may maintain several independent forwarding information databases (FIBs).
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The
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.Fn rtalloc
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family of routines is used by protocols to query this structure for a
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family of routines is used by protocols to query these structures for a
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route corresponding to a particular end-node address, and to cause
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certain protocol\- and interface-specific actions to take place.
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.\" XXX - -mdoc should contain a standard request for getting em and
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.\" en dashes.
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.Pp
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.Dv RTF_PRCLONING
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flag is obsolete and thus ignored by facility.
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If the
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.Dv RTF_XRESOLVE
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flag is set, then the
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.Dv RTM_RESOLVE
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message is sent instead on the
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.Xr route 4
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socket interface, requesting that an external program resolve the
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address in question and modify the route appropriately.
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The
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.Fn rtalloc1_fib
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function is the most general form of
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.Fn rtalloc ,
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and all of the other forms are implemented as calls to it.
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It takes a
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.Fa "struct sockaddr *"
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directly as the
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.Fa dst
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argument.
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The second argument,
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.Fa report ,
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controls whether the routing sockets are notified when a lookup fails.
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The third argument,
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.Fa flags ,
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is a combination of
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the following values:
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.Bl -item -offset indent
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.It
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.Dv RTF_RNH_LOCKED
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indicates that the radix tree lock is already held
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.El
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.Pp
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The default interface is
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.Fn rtalloc .
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Its only argument is
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The last argument
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.Fa fibnum
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specifies number of forwarding information database (FIB) on which
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the lookup should be performed.
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In case of success the
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.Fn rtalloc1_fib
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function returns a pointer to a locked
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.Vt "struct rtentry"
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with an additional reference.
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.Pp
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The
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.Fn rtalloc_fib
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is the most simple variant.
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Its main argument is
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.Fa ro ,
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a pointer to a
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.Dq Li "struct route" ,
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.Fa "struct route" ,
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which is defined as follows:
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.Bd -literal -offset indent
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struct route {
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struct sockaddr ro_dst;
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struct rtentry *ro_rt;
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struct llentry *ro_lle;
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struct sockaddr ro_dst;
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};
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.Ed
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.Pp
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Thus, this function can only be used for address families which are
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smaller than the default
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.Dq Li "struct sockaddr" .
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.Ft "struct sockaddr" .
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Before calling
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.Fn rtalloc
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.Fn rtalloc_fib
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for the first time, callers should ensure that unused bits of the
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structure are set to zero.
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The second argument
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.Fa fibnum
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is FIB number.
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In case of success of the
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.Fn rtalloc_fib
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the
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.Fa ro_rt
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points to a valid and unlocked
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.Xr rtentry 9 ,
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which has an additional reference put on it, freeing which is
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responsibility of the caller.
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On subsequent calls,
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.Fn rtalloc
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.Fn rtalloc_fib
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returns without performing a lookup if
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.Fa ro->ro_rt
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is non-null and the
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.Dv RTF_UP
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flag is set in the route's
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.Li rt_flags
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flag is set in the rtentry's
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.Fa rt_flags
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field.
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.Pp
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The
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.Fn rtalloc_ign
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interface can be used when the caller does not want to receive
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the returned
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.Fa rtentry
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locked.
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The
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.Fa ro
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argument is the same as
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.Fn rtalloc ,
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but there is additionally a
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.Fn rtalloc_ign_fib
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function is the same as the
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.Fn rtalloc_fib ,
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but there is additional
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.Fa flags
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argument, which is now only used to pass
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.Dv RTF_RNH_LOCKED
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indicating that the radix tree lock is already held.
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argument, which is same as in
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.Fn rtalloc1_fib .
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.Pp
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The
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.Fn RTFREE_LOCKED
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macro is used to unref and possibly free a locked routing entry
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with one our reference, for example previously allocated by
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.Fn rtalloc1_fib .
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.Pp
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The
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.Fn RTFREE
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macro is used to unref and possibly free an unlocked route entries with
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one our reference, for example previously allocated by
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.Fn rtalloc_fib
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or
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.Fn rtalloc_ign_fib .
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.Pp
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Both
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.Fn rtalloc
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.Fn RTFREE_LOCKED
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and
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.Fn rtalloc_ign
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functions return a pointer to an unlocked
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.Vt "struct rtentry" .
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.Pp
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The
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.Fn rtalloc1
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function is the most general form of
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.Fn rtalloc
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(and both of the other forms are implemented as calls to rtalloc1).
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It does not use the
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.Dq Li "struct route" ,
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and is therefore suitable for address families which require more
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space than is in a traditional
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.Dq Li "struct sockaddr" .
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Instead, it takes a
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.Dq Li "struct sockaddr *"
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directly as the
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.Fa sa
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argument.
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The second argument,
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.Fa report ,
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controls whether the lower layers are notified when a lookup fails.
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The third argument,
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.Fa flags ,
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is a set of flags to ignore, as in
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.Fn rtalloc_ign .
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The
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.Fn rtalloc1
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function returns a pointer to a locked
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.Vt "struct rtentry" .
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.Pp
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The
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.Fn rtfree
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function frees a locked route entry, e.g., a previously allocated by
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.Fn rtalloc1 .
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.Pp
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The
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.Fn RTFREE
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macro is used to free unlocked route entries, previously allocated by
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.Fn rtalloc
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or
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.Fn rtalloc_ign .
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The
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.Fn RTFREE
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macro decrements the reference count on the routing table entry (see below),
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and frees it if the reference count has reached zero.
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.Pp
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The preferred usage is allocating a route using
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.Fn rtalloc
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or
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.Fn rtalloc_ign
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and freeing using
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.Fn RTFREE .
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macros decrement the reference count on the routing table entry,
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and proceed with actual freeing if the reference count has reached zero.
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.Pp
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The
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.Fn RT_LOCK
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macro is used to lock a routing table entry.
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.Pp
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The
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.Fn RT_UNLOCK
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macro is used to unlock a routing table entry.
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@ -189,20 +192,53 @@ macro is used to unlock a routing table entry.
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The
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.Fn RT_ADDREF
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macro increments the reference count on a previously locked route entry.
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It should be used whenever a reference to an
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.Xr rtentry 9
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is going to be stored outside the routing table.
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.Pp
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The
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.Fn RT_REMREF
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macro decrements the reference count on a previously locked route entry.
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Its usage is contrary to
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.Fn RT_ADDREF .
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.Pp
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The
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.Fn rtfree
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function does the actual free of the routing table entry, and shouldn't
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be called directly by facilities, that just perform routing table lookups.
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.Sh LEGACY INTERFACE
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Prior to introduction of multiple routing tables functions did not
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require the
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.Fa "u_int fibnum"
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argument.
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Legacy
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.Fn rtalloc1 ,
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.Fn rtalloc
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and
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.Fn rtalloc_ign
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functions are kept for compatibility, and are equivalent to
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calling new interface with
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.Fa fibnum
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argument equal to
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.Va 0 ,
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which implies default forwarding table.
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.Sh RETURN VALUES
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The
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.Fn rtalloc ,
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.Fn rtalloc_ign
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and
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.Fn rtfree
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functions do not return a value.
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The
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.Fn rtalloc1
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function returns a pointer to a routing-table entry if it succeeds,
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.Fn rtalloc1_fib
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function returns a pointer to a locked routing-table entry if it succeeds,
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otherwise a null pointer.
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The
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.Fn rtalloc_fib
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and
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.Fn rtalloc_ign_fib
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functions do not return a value, but they fill in the
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.Fa *ro_rt
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member of the
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.Fa *ro
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argument with a pointer to an unlocked routing-table entry if they
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succeed, otherwise a null pointer.
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In a case of success all functions put a reference on the
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routing-table entry, freeing of which is responsibility of the caller.
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Lack of a route should in most cases be
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translated to the
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.Xr errno 2
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@ -213,7 +249,7 @@ value
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.Xr rtentry 9
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.Sh HISTORY
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The
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.Nm
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.Nm rtalloc
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facility first appeared in
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.Bx 4.2 ,
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although with much different internals.
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@ -227,14 +263,11 @@ first appeared in
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.Fx 2.0 .
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Routing table locking was introduced in
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.Fx 5.2 .
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Multiple routing tables were introduced in
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.Fx 8.0 .
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.Sh AUTHORS
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This manual page was written by
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.An Garrett Wollman ,
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as were the changes to implement
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.Dv RTF_PRCLONING
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and the
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.Fn rtalloc_ign
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function and the
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.Fa flags
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argument to
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.Fn rtalloc1 .
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The original version of this manual page was written by
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.An -nosplit
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.An "Garrett Wollman" .
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It was significantly updated by
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.An "Gleb Smirnoff" .
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